Field of the Invention
The present invention relates to sensing analyte concentration in a biological fluid, and more particularly to an optical sensor element for measuring analyte concentration in a biological fluid by optical means and a method of manufacture thereof.
Description of Related Art
Optical sensors using waveguides such as optical fibers are very useful in performing analyte assays in biological fluids. U.S. Pat. No. 5,859,937 issued Jan. 12, 1999 to Nomura, for example, describes a minimally invasive medical testing device and method for its use which utilizes a light-conducting optical fiber sensor element having a localized textured site thereon, wherein a reagent is deposited. Interaction of the reagent with an analyte specific to the reagent produces a response, such as development of a colored product, which is detectable by means of a change in characteristics of a light beam transmittable through the optical fiber. By means of the textured site and its increased surface area, the sensitivity of the medical testing device is greatly enhanced. The sensor is particularly useful in blood glucose determinations, requiring smaller blood samples than flat strip devices. Improvements in such optical fiber sensor elements have even further increased their sensitivity. Examples of such improved optical fiber sensor elements may be found in, for example, United States Published Patent Application No. 2009/0219509 published Sep. 3, 2009 in the name of Nomura, United States Published Patent Application No. 2011/0097755 published Apr. 28, 2011 in the name of Nomura, and U.S. Pat. No. 8,008,068 issued Aug. 30, 2011 to Nomura.
The handling of individual optic fibers during manufacture is not without difficulty in a practical industrial process. Steps would normally include cutting optic fibers into short lengths, attaching them to some form of belt or carrier, exposing a belted bundle or continuous array of optic fiber ends to an etchant such as a stream of atomic oxygen gas, then depositing a mixture of analyte-reactive reagent and hollow polymeric particles on the treated tips, followed by drying and repositioning of such treated fibers into cartridges for use by a consumer such as a diabetic patient. Improvements in optical sensor elements to enhance their manufacturability and improvements in the methods of manufacture thereof are desirable.